There has been proposed a typical vane compressor described below (see, for example, Patent Literature 1). The vane compressor includes a rotor shaft (an integrated unit of a cylindrical rotor portion that rotates in a cylinder and a shaft that transmits a rotational force to the rotor portion), and a vane received in each of one or more vane grooves in the rotor portion. The vane slides while its tip is in contact with the inner circumferential surface of the cylinder. The cylinder includes a discharge port extending in a radial direction and disposed in its inner circumferential surface at a location that is near the finish of the discharge stroke and that has a large phase angle.
There has also been proposed a vane compressor including an auxiliary discharge port to reduce the loss caused by excessive compression of discharge gas remaining in a narrow space after passing through a discharge port (see, for example, Patent Literature 2). The auxiliary discharge port extends in a radial direction and disposed in the inner surface of the cylinder at a location having a phase angle larger than that at the above-described discharge port (hereinafter referred to as first discharge port) (that is, at a location downstream of the first discharge port in the direction of rotation of the vane and downstream in the compression stroke), the location being near the first discharge port.